1. Technical Field
The present invention relates to an inertial sensor.
2. Description of the Related Art
Recently, an inertial sensor has been used as various applications, for example, military such as an artificial satellite, a missile, an unmanned aircraft, or the like, vehicles such as an air bag, electronic stability control (ESC), a black box for a vehicle, or the like, hand shaking prevention of a camcorder, motion sensing of a mobile phone or a game machine, navigation, or the like.
The inertial sensor generally adopts a configuration in which a mass body is adhered to an elastic substrate such as a membrane, or the like, in order to measure acceleration and angular velocity. Through the configuration, the inertial sensor may calculate the acceleration by measuring inertial force applied to the mass body and may calculate the angular velocity by measuring Coriolis force applied to the mass body.
In detail, a scheme of measuring the acceleration and the angular velocity using the inertial sensor is as follows. First, the acceleration may be calculated by Newton's law of motion “F=ma”, where “F” represents inertial force applied to the mass body, “m” represents a mass of the mass body, and “a” is acceleration to be measured. Among others, the acceleration a may be obtained by sensing the inertial force F applied to the mass body and dividing the sensed inertial force F by the mass m of the mass body that is a predetermined value. Further, the angular velocity may be calculated by Coriolis force “F=2 mΩ×v”, where “F” represents the Coriolis force applied to the mass body, “m” represents the mass of the mass body, “Ω” represents the angular velocity to be measured, and “v” represents the motion velocity of the mass body. Among others, since the motion velocity V of the mass body and the mass m of the mass body are values known in advance, the angular velocity Ω may be calculated by detecting the Coriolis force F applied to the mass body.
Meanwhile, the inertial sensor according to the prior art includes a piezoelectric body that is formed above a membrane (diagram) so as to drive a mass body, as disclosed in Korean Laid-Open Patent No. 10-2011-0072229. Here, the piezoelectric body drives the membrane in a specific direction (for example, an X-axis direction or a Y-axis direction). In this case, unbalance may occur during the general driving due to a non-uniform thickness of the membrane, mis-alignment of a piezoelectric body or an electrode, or the like. Therefore, it is difficult for the piezoelectric body to drive the membrane only in a desired specific direction. That is, even though the piezoelectric body vibrates the membrane in an X-axis direction, a wave is propagated in an undesired direction causing unbalance during the general driving, such that the membrane is vibrated out of a predetermined angle in an X-axis direction. As described above, when the membrane is not driven in the desired specific direction, sensitivity of the inertial sensor may be finally degraded.